Hello People, I understand there are 3 style taps .. Taper, Plug, and Bottoming. What I need to know is whether or not using a "bottoming tap", IF a NEW Thread can be cut from Scratch ? I believe this tap is primarly used to "clean-up" a thread, rather than cut a new one. Thanks People, Nitro.
Hand tap styles
- Thread starter NITRO-BTU
- Start date
chad s
Well-known member
A bottoming tap is not used to clean threads, thats a re-threading tap, which pushes metal, not cutting. (btw, thread cutting taps, all 3 variants should not be used to chase threads, they can damage them)
A bottoming tap is used after a plug tap when the absolute bottom of a blind hole needs threrads all the way to the end. Since a plug tap has the last 3 or so threads tapered to help start it, it doesnt cut full threads at the very end.
Cuttung a new thread with a bottoming tap will be extremely hard by hand, if possible at all. You also probably rusk breaking the tap much easier.
voidifused
Well-known member
Also with out having the tapper of the tap you are more likely to cross thread the part you are working with, as well as mawl the top off the hole trying to get it to start.
-B-
Well-known member
This may help you you need three taps to do it right. http://ase.tufts.edu/mechanical/shop/classes/me1/threading.htm
tatra
Well-known member
been using bottoming taps for years on locomotive engines and can honestly say that thread damage hasn't been a problem, for the most part............taps from 1/4" to 1 1/2 " are used routinely throughout the locomotive when needed and no probs to justify chasing taps...... that i can see..........not saying that what we do is right or better but seems to work ok................what is the issue with using a bottoming tap as a chaser?........seems to me it would just follow the original threads,no?.........
voidifused
Well-known member
been using bottoming taps for years on locomotive engines and can honestly say that thread damage hasn't been a problem, for the most part............taps from 1/4" to 1 1/2 " are used routinely throughout the locomotive when needed and no probs to justify chasing taps...... that i can see..........not saying that what we do is right or better but seems to work ok................what is the issue with using a bottoming tap as a chaser?........seems to me it would just follow the original threads,no?.........
I use them to chase holes all the time, using them to cut new threads in a piece which has no threads existing i believe what the OP was applying.
I have a set of chasers, i mostly use them were you can not get a tap wrench or die holder so you can just ratchet them though, mine are here
http://buy1.snapon.com/catalog/item...=56049&group_ID=1148&store=canada&dir=catalog
tatra
Well-known member
i have and will still use one if there is no other choice but to try and get the job done , but will not appologize if using a bottoming tap is all i have at my disposal to cut tnew threads. if told to do so by the boss..........being the boss and making more than me he knows more better than me obviously, right?........on my own stuff, i'll get the proper tools and equipment and do it later.........as for clearance issues, we also hardly ever use tap handles when chasing threads,,,,,,,,,just press a nut on the square drive of the tap required and use an air ratchet or even impact gun........not saying broken taps don't happen but the time saved and the numbe rthat do break far outweigh the cost of replacement and time to remove the broken one.........of course after doing it for over 20 years you get a feel for it too..........not text book approved but it does work in the field..........
voidifused
Well-known member
speed bump
Well-known member
i have and will still use one if there is no other choice but to try and get the job done , but will not appologize if using a bottoming tap is all i have at my disposal to cut tnew threads. if told to do so by the boss..........being the boss and making more than me he knows more better than me obviously, right?........on my own stuff, i'll get the proper tools and equipment and do it later.........as for clearance issues, we also hardly ever use tap handles when chasing threads,,,,,,,,,just press a nut on the square drive of the tap required and use an air ratchet or even impact gun........not saying broken taps don't happen but the time saved and the numbe rthat do break far outweigh the cost of replacement and time to remove the broken one.........of course after doing it for over 20 years you get a feel for it too..........not text book approved but it does work in the field..........
I ran into some taps with bolts on them the other day and wondered if that was why they had them on there.
Personally I always use taps to chase holes and have never had a problem, you just have to know what feels right and what doesn't.
Hello Chad, 33 % of the People in the Poll indicated that a Bottoming Tap could cut new threads from scratch. WHAT SAY YOU ABOUT THAT ?
kythri
Well-known member
Hello Chad, 33 % of the People in the Poll indicated that a Bottoming Tap could cut new threads from scratch. WHAT SAY YOU ABOUT THAT ?
And 50% say no.
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Stuey
Well-known member
Chad right, you wrong. It doesn't matter how many people say you can; what matters is how many people know that you should not.
Hello Chad, 33 % of the People in the Poll indicated that a Bottoming Tap could cut new threads from scratch. WHAT SAY YOU ABOUT THAT ?
speed bump
Well-known member
I had to cut some threads with a bottoming tap yesterday and while its a pain it can definitely be done you just have to watch that you get the tap in the hole correctly to start.
voidifused
Well-known member
Hello Chad, 33 % of the People in the Poll indicated that a Bottoming Tap could cut new threads from scratch. WHAT SAY YOU ABOUT THAT ?
If its a 4500$ part would you take the 33% chance or would you get the right tool for the job? Just because it "can" does not mean you should.
You can use a screwdriver for chisel and it will work but would you do it?
Merkava_4
Banned
Bottoming taps are used to cut threads all the way to the bottom of blind holes. Taper taps and plug taps are often considered the same. Usually the 3 types of hand taps are gun taps, plug taps, and bottoming taps. I don't know who starting calling them "taper" taps because if you look at them, they're all tapered to some degree. Gun taps are the easiest to start cutting threads with, but they are primarily used for through holes.
voidifused
Well-known member
Its been a while since i heard some one call them a gun tap. Even in my new KBC catalog calls them a taper tap. http://www.kbctools.com/
Merkava_4
Banned
voidifused
Well-known member
I'm an old dude, that's why.
Hey, you said it. I was trying to beat around that fact
Kevin54
MEMBER EMERITUS
Its been a while since i heard some one call them a gun tap. Even in my new KBC catalog calls them a taper tap. http://www.kbctools.com/
It depends on where you get the tap from. When I order them for my department I order Gun Taps and have specified them that way for years.
If you try to thread a hole with a smaller bottom tap, you will snap the tap off. You need a more aggressive lead on the tap to keep that from happening. Normally a bottom tap is used to finish off what a plug tap has done. But material also makes a difference. In soft material you may get by with a bottom tap to start out and thread the hole. In steel and some exotic metals, it will probably break if the tap size is under a 1/4"
Check this out to see different tap styles and their usage. http://www.newmantools.com/taps/styles.htm But as I stated before, different companies list different styles of taps but this covers quite an array. It does not list a Gun tap. This site does http://www.discount-tools.com/catalogs/gen/industrial.cfm?page=85 And with taps there is a certain amount of science to it. There are different classifications of Pitch diameter limits. This determines how tight or loose a bolt may be in a threaded hole. At work we normally use a GH3 Pitch diameter limit. That is just about your basic thread. For some specifications for Government work we had a classification of H1 or H2 and all had to be checked with calibrated Go-No Go thread gages.
Then you can get into Roll Taps. Those styles do not cut a thread, but they cold form it into the metal.
For a good basic tap for most holes, a 2 flute pointed gun tap will serve the purpose with a GH-3 classification. If you think you are going to run threads to the bottom of holes, then get a bottoming tap (finishing tap) Unless you are working with materials of a specific thickness a pointed tap usually suffices.
And as far as the number of flutes.......two flutes give more chip clearance, three flutes make it easier to keep the tap aligned if doing it by hand, and four flutes are not worth it at all. For small taps you want a two flute, 3/8" taps usually go to a three flute, anything under a 1/4" size and a four flute you really risk breakage.
As far as purchasing taps, always buy new if you can. Never trust a used tap unless it is your own. All it take is one tooth to break off of a tap in a threaded hole and it can lock it in tight. When you go to back it out it will snap. Proper lubricant is a must also. Different materials use different lubricants. What may be good for cast iron will not be good for aluminum and visa versa.
Sorry to go on, but I have removed hundreds, if not a few thousand broken taps over the years and have tapped thousand upon thousands of holes. A broken tap usually results from one of three things.....the wrong tap for the job, operator error, or a dull tap.
voidifused
Well-known member
Some nice links, thanks for the cool info Kevin54 
Atlascycle
Well-known member
the poll asks will a bottoming tap cut a new thread....yes it will....should you use a bottoming tap to cut a new thread....No.
Using the right tool for the job will achieve the best results. Take head to Kevin’s remarks. He knows what he’s talking about. Hmmm,, must be a tool maker....
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